Nef is a key protein involved in the pathway of HIV infectivity. Nef binds to the SH3 domain of the Src family of kinases, although its role in infectivity is still unclear. Using a newly developed assay for Nef-SH3 binding the investigators will use high-throughput screening of 40,000 fungal extracts for binding to the Nef-SH3 complex. After confirmation of activity, active extracts will be selected for initial purification and characterization of active principles.